Hepadnaviridae

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A Viral Biorealm page on the family Hepadnaviridae

Baltimore Classification

Higher order taxa

Virus; Retro-transcribing viruses; Hepadnaviridae

Genera

Orthohepadnavirus, Avihepadnavirus

Description and Significance

The name "Hepadnaviridae" is derived from the Latin word hepa, meaning "liver", due to the liver infections this family of viruses causes. Members of the Hepadnaviridae family are pararetroviruses, and as such are classified with Retroviruses and Caulimoviruses in the genome group of retro-transcribing viruses. Hepatitis B virus, in the genus Orthohepadnavirus, has caused an estimated 350 million chronic cases worldwide. (sources: Pult et al., Aiba et al.)

Genome Structure

The Hepadnaviridae genome is non-segmented and consists of a single molecule of open circular, partially double-stranded DNA containing extensively overlapping genes. The full-length strand of DNA is 3020-3320 nucleotides long, and the short-length strand is 1700-2800 nucleotides long. The genome codes for both structural and non-structural proteins. (source: ICTVdB, Pult et al.)

Virion Structure of a Hepadnavirus

Hepadnaviridae virions consist of an envelope and a nucleocapsid, and are 40-48nm in diameter. The virions are spherical or pleomorphic, although filamentous forms can occur. Spherical forms without cores can also occur. The nucleocapsid is round, exhibits icosahedral symmetry, and is 30-35nm in diameter. The capsid consists of 180 capsomers. (source: ICTVdB)

Reproduction Cycle of a Hepadnavirus in a Host Cell

Replication of all members of this family involves reverse transcription of an RNA intermediate. (source: Pult et al.)

Viral Ecology & Pathology

Hepadnaviruses infect a wide variety of species, causing liver infections. In humans, Hepatitis B virus causes new infections in nearly 60,000 people per year. Hepadnaviruses also infect rodents such as woodchucks and squirrels, old and new world primates such as wooly monkeys and gibbons, and in birds (most notably in ducks, but also in gray herons and snow geese). (sources: CDC, Pult et al.)

References

Aiba et al. "Complete Nucleotide Sequence and Phylogenetic Analyses of Hepatitis B Virus Isolated from Two Pileated Gibbons." Virus Genes 27.3 (2003): 219-226.

Centers for Disease Control and Prevention. Viral Hepatitis B Fact Sheet.

ICTVdB - The Universal Virus Database, version 3. http://www.ncbi.nlm.nih.gov/ICTVdb/ICTVdB/

Pult et al. "Identification and Analysis of a New Hepadnavirus in White Storks." Virology 289.1 (2001): 114-128.